Thermal engines, for example Stirling engines, have been known for a long time and offer a possibility of converting thermal energy into mechanical work, wherein a very high degree of efficiency is possible, and with long maintenance-free operating times owing to the type of construction.
Although such thermal engines which are known hitherto have advantages such as the lack of restriction to a particular heat source, these are not yet used commercially on a larger scale because the efficiency of the thermal engines is still very far removed from the efficiency of internal combustion engines.
The document EP0850353 discloses thermal engines in the form of a Stirling engine, wherein the working medium runs through a circulation process in which thermal energy is partially converted into mechanical work.
A plurality of chambers in cylinder form and pistons are provided, which are mechanically coupled with each other, wherein the pistons move substantially in phase opposition with respect to each other during operation. Through an alternating heating, by means of heat exchangers, and cooling, by means of cooling devices, of a working medium within the chambers, pistons are able to be moved to and fro linearly in a corresponding manner. The linear movement of the pistons is converted by a mechanical coupling by means of a wobble plate into a rotary movement. The wobble plate drives a drive shaft which is able to be connected mechanically with a load. To increase the efficiency, various steps were taken, for example the sealing of the pistons was improved. By a suitable choice of high temperature materials for the chambers and pistons, the temperature difference between the hot side of the heat exchangers and the cold side of the cooling devices was able to be increased without danger, whereby the resulting mechanical work was increased.
The improvement to the operation of the thermal engine of EP0850353 was achieved by means to set the piston stroke and the wobble disc angle. These means are embodied electrically and lead to the thermal engine having to be equipped with a motor and further components. Such thermal engines are therefore more complex and embodied with a plurality of components, whereby they are more complicated to operate and are more liable to error.
Hitherto, to optimize the heat conduction or heat transmission to the working medium, the working medium is guided through a plurality of thin small tubes with a large overall surface outside the chambers, with the thermal energy being transferred. In order to achieve higher outputs, the operating pressure had to be increased accordingly, from which a mechanical stressing of the plurality of small tubes results.